n = int(input())
s = set()
for k in range(n):
    help_set = set()
    a = input().split()
    x1, y1, x2, y2 = [int(z) for z in a]
    for i in range(x1, x2):
        for j in range(y1, y2):
            help_set.add((i, j))
    s = s.union(help_set)
print(len(s))